renumbering values in .pdb file

I have one .pdb file, which correspond to peptide-protein complex. Fragment of this file looks like this:

^{edit: replaced the sample input with a subset of what OP provided afterwards.}

ATOM     51  O   ARG     4      18.189  21.505 -30.356  0.00  0.00
ATOM     52  OXT ARG     5      19.822  21.322 -27.773  0.00  0.00
TER
ATOM      1  N   MET A   1      -9.976  22.279  65.378  1.00 37.35           N
ATOM      2  H   MET A   1      -9.180  21.915  65.882  1.00 37.35           H
ATOM      3  N   LYS A   2     -11.970  21.837  62.804  1.00 40.65           N
ATOM      4  H   LYS A   2     -11.194  21.438  62.295  1.00 40.65           H

I want change numeration 6th column for all lines directly after first "TER" line in my .pdb file. Now, numeration in 6th column start from 1 but I want, that numeration in 6th column started in the same way as above, but started with 6 instead of 1.

Additionally, I want change numeration in 2nd column for all lines also directly after first "TER" line in my .pdb file. Now, numeration in 2nd column start from 1 but I want, that numeration in 2nd column started in the same way as above, but started with 53 instead of 1.

_{edit: added an expected output that illustrates OP's original goal.}

The expected output would be:

ATOM 51 O ARG 4 18.189 21.505 -30.356 0.00 0.00
ATOM 52 OXT ARG 5 19.822 21.322 -27.773 0.00 0.00
TER
ATOM 53 N MET A 6 -9.976 22.279 65.378 1.00 37.35 N
ATOM 54 H MET A 6 -9.180 21.915 65.882 1.00 37.35 H
ATOM 55 N LYS A 7 -11.970 21.837 62.804 1.00 40.65 N
ATOM 56 H LYS A 7 -11.194 21.438 62.295 1.00 40.65 H

Can You help me ?

I tried doing this by using bash script, but when I'm opening my edited .pdb file in Pymol I have something like this

This is my code:

#!/bin/bash

# read input file and output file names from command line arguments
input_file=complex.pdb
output_file=renum.pdb

# initialize residue counter and flag for tracking first "TER" occurrence
residue_num=1
ter_found=false

# loop through the lines of the input file
while read line
do
    # check if the line contains "TER"
    if [[ "$line" == "TER" ]]
    then
        # if it does, reset the residue counter to 5 and set the flag to true
        residue_num=5
        ter_found=true
    else
        # if it doesn't, extract the residue name and chain ID from the line
        residue_name=$(echo $line | awk '{print $4}')
        chain_id=$(echo $line | awk '{print $5}')

        # if the residue name or chain ID has changed, increment the residue counter
        if [[ "$residue_name" != "$prev_residue_name" || "$chain_id" != "$prev_chain_id" ]]
        then
            residue_num=$((residue_num+1))
        fi

        # if the first "TER" has been found, replace the 6th column with the new residue number
        if [[ "$ter_found" == true ]]
        then
            line=$(echo $line | awk -v num="$residue_num" '{$6=num; print}')
        fi

        # save the current residue name and chain ID for comparison in the next iteration
        prev_residue_name=$residue_name
        prev_chain_id=$chain_id
    fi

    # write the modified line to the output file
    echo $line >> $output_file
done < $input_file

Finally my renum.pdb file looks like this (this is only fragment this .pdb file):

^{edit: The following output was generated by processing the "updated" input with OP's code.}

ATOM 51 O ARG 4 18.189 21.505 -30.356 0.00 0.00
ATOM 52 OXT ARG 5 19.822 21.322 -27.773 0.00 0.00
TER
ATOM 1 N MET A 6 -9.976 22.279 65.378 1.00 37.35 N
ATOM 2 H MET A 6 -9.180 21.915 65.882 1.00 37.35 H
ATOM 3 N LYS A 7 -11.970 21.837 62.804 1.00 40.65 N
ATOM 4 H LYS A 7 -11.194 21.438 62.295 1.00 40.65 H

A PDB has fixed-width columns, so you shouldn't transform it into a single-space delimited file because the other programs won't be able to process it afterwards.

For an ATOM record, the specification is:

For processing it with any awk, you can use substr to extract the relevant parts:

awk '
    /^TER/  { after_TER = 1 }
    /^ATOM/ {
        if (after_TER) {
            resName = substr($0,18,3)
            if ( resName != previous_resName ) {
                previous_resName = resName
                resSeq = sprintf("%4d", resSeq + 1)
            }
            $0 = substr($0,1,6) \
                 sprintf("%5d", ++serial) \
                 substr($0,12,11) \
                 resSeq \
                 substr($0,27)
        } else {
            serial = substr($0,7,5)
            resSeq = substr($0,23,4)
        }
    }
    { print }
' mod.pdb > renum.pdb

Example

Input:

ATOM     51  O   ARG     4      18.189  21.505 -30.356  0.00  0.00
ATOM     52  OXT ARG     5      19.822  21.322 -27.773  0.00  0.00
TER
ATOM      1  N   MET A   1      -9.976  22.279  65.378  1.00 37.35           N
ATOM      2  H   MET A   1      -9.180  21.915  65.882  1.00 37.35           H
ATOM      3  N   LYS A   2     -11.970  21.837  62.804  1.00 40.65           N
ATOM      4  H   LYS A   2     -11.194  21.438  62.295  1.00 40.65           H

Output:

ATOM     51  O   ARG     4      18.189  21.505 -30.356  0.00  0.00
ATOM     52  OXT ARG     5      19.822  21.322 -27.773  0.00  0.00
TER
ATOM     53  N   MET A   6      -9.976  22.279  65.378  1.00 37.35           N
ATOM     54  H   MET A   6      -9.180  21.915  65.882  1.00 37.35           H
ATOM     55  N   LYS A   7     -11.970  21.837  62.804  1.00 40.65           N
ATOM     56  H   LYS A   7     -11.194  21.438  62.295  1.00 40.65           H